Radial roller heads became known, for example, from DE 24 41 387 A1, DE 42 36 085 A1 or also EP 0 853 991 B1. The radial roller heads have in common that rollers are arranged in a distributed manner around the roller axis in a holder under the same angle and axis-center distances. The roller surfaces have a spiral rising progression around the perimeter in a counter-clockwise manner. The rollers are coupled with a gear-wheel drive, and a locking device automatically engages after each full roller rotation. The locking device is triggered before the roller procedure and namely by the work piece that is to be formed with the roller or also by an actuating lever. The rollers are driven with the help of several tension springs, which engage eccentrically on a disk. The disk is connected in a torque-proof manner with a cam plate, which in turn works together with a locking element. During the rotation of the rollers through contact with the work piece, the springs are tensioned and locked in their tensioned position through contact of the locking element with the cam plate. Only after the release of the locking device does a partial rotation of the rollers take place from a position, in which the work piece can be readily inserted axially between the rollers, to a position in contact with the work piece.
An automatic release of the locking device became known from the named EP 0 853 991 B1 in which the work piece hits a pin and the unlocking is thereby set in motion. The mechanism required for this is relatively complicated.